1. Field of the Invention
The present invention relates to a liquid discharge head including a piezoelectric substrate.
2. Description of the Related Art
A liquid discharge head for discharging ink is generally mounted onto an ink jet recording apparatus for recording an image on a recording medium by discharging the ink. As a mechanism for causing the liquid discharge head to discharge ink, there is known a mechanism using a pressure chamber that is formed of a piezoelectric element and is changeable in volume to be shrinkable. In this mechanism, the pressure chamber shrinks due to the deformation of the piezoelectric element to which a voltage is applied, and thus the ink inside the pressure chamber is discharged from a discharge orifice formed at one end of the pressure chamber. As one liquid discharge head including such a mechanism, there is known a shear mode liquid discharge head. In the shear mode liquid discharge head, one or two inner wall surfaces of the pressure chamber are formed of the piezoelectric element, and the pressure chamber is caused to shrink by shear deformation of the piezoelectric element instead of extension or contraction deformation thereof.
Regarding liquid discharge apparatus for industrial applications or the like, there is a demand for use of high viscosity liquid. In order to discharge high viscosity liquid, a large discharge force is required for the liquid discharge head. To satisfy this demand, there has been proposed a liquid discharge head called a Gould type, in which the pressure chamber is formed of a tubular piezoelectric element having a circular or rectangular sectional shape. In the Gould type liquid discharge head, the piezoelectric element extends or is deformed by contraction in the inward and outward directions (radial direction) about the center of the pressure chamber. In this manner, the pressure chamber expands or shrinks. In the Gould type liquid discharge head, the entire wall surface of the pressure chamber deforms, and this deformation contributes to the ink discharge force. Therefore, as compared to the shear mode liquid discharge head in which one or two wall surfaces are formed of the piezoelectric element, a larger ink jet force can be obtained.
In a Gould type liquid discharge head, in order to obtain a higher resolution, it is necessary to arrange multiple discharge orifices more densely. This involves the necessity of densely arranging pressure chambers corresponding to the discharge orifices, respectively. The method of manufacturing a Gould type liquid discharge head capable of arranging pressure chambers with high density is disclosed in Japanese Patent Application Laid-Open No. 2007-168319.
In the manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2007-168319, first, multiple grooves all extending in the same direction are formed in each of multiple piezoelectric substrates. After that, the multiple piezoelectric substrates are stacked so that the grooves are directed in the same direction, and are cut in a direction orthogonal to the direction of the grooves. The groove part of the cut piezoelectric substrate forms an inner wall surface of the pressure chamber. After that, in order to separate the respective pressure chambers, the piezoelectric substrate present between the pressure chambers is removed to a certain depth. On upper and lower sides of the piezoelectric substrate having the completed pressure chambers, a supply path plate and an ink pool plate, and a printed circuit board and a nozzle plate are respectively connected. In this manner, the liquid discharge head is completed. With this manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2007-168319, the pressure chambers can be arranged in matrix, and hence the pressure chambers can be arranged in high density. Further, with this manufacturing method, because forming a groove in the piezoelectric substrate is better in processing than opening a hole in the piezoelectric substrate, the pressure chambers can be formed with high accuracy.
In the liquid discharge head manufactured by the manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2007-168319, multiple pressure chambers are arranged with space therebetween. Therefore, in particular, when the length (height) of the pressure chambers is increased in order to discharge highly viscous liquid (in order to increase the liquid discharge force), the stiffness of the liquid discharge head is lowered. When the stiffness is lowered, a piezoelectric substrate which forms the pressure chambers may be broken and liquid cannot be discharged therefrom.
Accordingly, an object of the present invention is to provide a liquid discharge head which solves the above-mentioned problem. The liquid discharge head which can endure to repeatedly discharge highly viscous ink irrespective of the length of a unit stack, and includes a unit stack having densely arranged ink discharging portions.
Accordingly, an object of the present invention is to provide a liquid discharge head which can enhance the stiffness of a piezoelectric substrate forming a pressure chamber, and a manufacturing method therefor.